State Key Laboratory of Microbial Technology, Shandong University, Jinan, People's Republic of China.
PLoS One. 2011 Apr 20;6(4):e19030. doi: 10.1371/journal.pone.0019030.
Phenyllactic acid (PLA), a novel antimicrobial compound with broad and effective antimicrobial activity against both bacteria and fungi, can be produced by many microorganisms, especially lactic acid bacteria. However, the concentration and productivity of PLA have been low in previous studies. The enzymes responsible for conversion of phenylpyruvic acid (PPA) into PLA are equivocal.
METHODOLOGY/PRINCIPAL FINDINGS: A novel thermophilic strain, Bacillus coagulans SDM, was isolated for production of PLA. When the solubility and dissolution rate of PPA were enhanced at a high temperature, whole cells of B. coagulans SDM could effectively convert PPA into PLA at a high concentration (37.3 g l(-1)) and high productivity (2.3 g l(-1) h(-1)) under optimal conditions. Enzyme activity staining and kinetic studies identified NAD-dependent lactate dehydrogenases as the key enzymes that reduced PPA to PLA.
CONCLUSIONS/SIGNIFICANCE: Taking advantage of the thermophilic character of B. coagulans SDM, a high yield and productivity of PLA were obtained. The enzymes involved in PLA production were identified and characterized, which makes possible the rational design and construction of microorganisms suitable for PLA production with metabolic engineering.
苯乳酸（PLA）是一种新型抗菌化合物，对细菌和真菌具有广谱而有效的抗菌活性，可由许多微生物产生，尤其是乳酸菌。然而，在以前的研究中，PLA 的浓度和产量一直很低。负责将苯丙酮酸（PPA）转化为 PLA 的酶尚不清楚。
方法/主要发现：为了生产 PLA，我们分离到了一种新型嗜热菌株凝结芽孢杆菌 SDM。当 PPA 的溶解度和溶解速率在高温下得到增强时，凝结芽孢杆菌 SDM 的完整细胞可以在最佳条件下以 37.3 g l(-1) 的高浓度和 2.3 g l(-1) h(-1) 的高生产率有效地将 PPA 转化为 PLA。酶活性染色和动力学研究鉴定 NAD 依赖性乳酸脱氢酶为将 PPA 还原为 PLA 的关键酶。
结论/意义：利用凝结芽孢杆菌 SDM 的嗜热特性，我们获得了 PLA 的高产率和高生产率。鉴定并表征了参与 PLA 生产的酶，这使得通过代谢工程合理设计和构建适合 PLA 生产的微生物成为可能。
